1. Field of the Invention
The present invention relates to a poppet type directional control valve driven by pilot pressure.
2. Discussion of the Background
A poppet type directional control valve is already known, which comprises a supply port for pressure fluid opened to a valve bore where a valve disc is to be inserted, output port opened to said valve bore and with communication to said supply port being blocked when the valve disc is switched over, a discharge port opened to said valve bore and being communicated with the output port when the communication between the supply port and the output port is blocked, and a pilot port opened to a pilot chamber at one end of the valve bore, whereby a first valve seat and a second valve seat are provided between the supply port and the output port and between the output port and the discharge port respectively in said valve bore, there are provided a valve body integrated with these valve seats and a poppet type valve disc to be inserted into said valve bore open or close the first and the second valve seats, said valve disc is switched over by pilot fluid pressure supplied from or discharged to the pilot chamber, and the first and the second valve seats are opened or closed by the pilot fluid pressure.
In the directional control valve already known as described above, a valve disc is designed as a poppet type sealing member for opening and closing valve seats mounted on a flange, which is usually formed by cutting a valve rod or fitting on it.
However, the above directional control valve is disadvantageous in that the arrangement and assembling of the valve body and valve disc are not very easy and simple. The flange has to be manufactured by cutting the valve rod or fitting on the valve rod, and this results in much labor and cost in the manufacture. Because the diameter of the poppet type sealing member is larger than the diameter of the valve seat in the valve body, the insertion of the valve disc into or assembling on the valve bore are very troublesome. Further, the piston for switching over and driving the valve disc must be airtightly inserted in the pilot cheer, and this means an increase in the number of processes in the assembling procedure.
It is a principal object of the present invention to provide a poppet type directional control valve, in which it is possible to mold the valve body and to mold and assemble the valve disc in a simple and easy manner and to manufacture these components at low cost.
It is another object of the present invention to provide a poppet type directional control valve, in which the poppet type valve disc has a very simple arrangement and there is no need to mount a poppet type sealing member on a flange formed by cutting a valve rod or by fitting on it.
It is still another object of the present invention to provide a poppet type directional control valve, in which the number of processes in the assembling procedure is reduced and there is no need to airtightly insert a piston for switching over and driving the valve disc into a pilot chamber.
To attain the above objects, the poppet type directional control valve according to the present invention has a valve body, which comprises a supply port, an output port, a discharge port and a pilot port opened to a valve bore, and a poppet type valve disc is switched over and driven by pilot fluid pressure to a pilot cheer, whereby said valve bore of the valve body comprises a first valve bore formed from one end in axial direction of the valve body via an opening of the supply port toward a first valve seat, a second valve bore formed from the other end in axial direction of the valve body via the pilot chamber and an opening of the discharge port toward a second valve seat, and a communicating valve bore located between the first valve seat and the second valve seat positioned back-to-back to each other and formed from the first valve bore and the second valve bore via an opening of the output port and for communicating these valve bores with each other, the poppet type valve disc comprises a first valve disc inserted through the first valve bore and used for opening and closing the first valve seat, and a second valve disc inserted through the second valve bore, connected integrally with the first valve disc and used for opening and closing the second valve seat, these components being made of a material having elasticity and a sealing property, each component being integrally molded, and said pilot chamber is formed between the second valve disc airtightly inserted into the second valve bore and a closing member for closing an opening of the second valve bore.
In the poppet type directional control valve as described above, a guide for guiding the second valve disc to move in the second valve bore can be integrally provided on the second valve bore or the second valve disc, and the closing member for closing the opening of the second valve bore can be formed as a manual operating member for switching over and driving the valve disc by pressure from outside. Further, in order to introduce output of a small sized solenoid valve into the pilot port and to utilize output of the poppet type directional control valve as pilot fluid for driving a main valve having a large capacity, a supply port, an output port and a discharge port for pressure fluid are opened on a main valve mounting surface on one side of the valve body, and a supply hole and a discharge hole directly communicated with the supply port and the discharge port respectively and a pilot port communicated with the pilot chamber are formed on a solenoid valve mounting surface on the opposite side.
In the poppet type directional control valve with the above arrangement, when the pilot fluid is supplied to or discharged from the pilot chamber, the first valve disc and the second valve disc are integrally moved in the valve bore by the pilot fluid pressure applied on the second valve disc. Thus, it is possible to switch over the communication between the output port or the supply port and the discharge port. In this case, the second valve disc is moved in the second valve bore as it is guided by a guide provided on the second valve bore or on the valve disc itself. Thus, the valve disc can be switched over and driven in stable manner.
When the manual operating member is pushed from outside the valve body, the valve disc is integrally moved, and this makes it possible to switch over the communication between the ports by manual operation.
In the poppet type directional control valve as described above, the valve bore of the valve body comprises a first valve bore formed from one end in axial direction toward the first valve seat, a second valve bore formed from the other end in axial direction via the pilot chamber toward the second valve seat, and a communicating valve bore located between the first valve seat and the second valve seat, formed from the first valve bore and the second valve bore and used for communicating the first and the second valve bores with each other. Accordingly, the valve bores on the valve body can be easily formed, and the valve disc can be easily inserted from both ends in axial direction. Thus, the poppet type valve disc can be easily assembled after formation of the valve body.
In the directional control valve of the present invention, the first valve disc is inserted into the first valve bore from one end in axial direction and the second valve disc is inserted into the second valve bore from the other end. These valve discs are connected at intermediate portion, and there is no need to mount a poppet type sealing member on a flange, which is formed by cutting a valve rod or fitting on it. Thus, the valve discs can be molded in simple and easy manner and can be produced at low cost. Moreover, there is no need to insert the piston for switching over and driving the valve disc separately into the pilot chamber, and this makes it possible to reduce the number of processes in the assembling procedure.
Further, the supply port, the output port and the discharge port are provided on a main valve mounting surface on one side of the valve body, and a supply hole and a discharge hole directly communicated with the supply port and the discharge port respectively and a pilot port communicated with the pilot chamber are provided on a solenoid valve mounting surface on the opposite side. As this poppet type directional control valve is used as a valve for amplifying the pilot fluid, compared with a small size pilot solenoid valve mounted on the solenoid valve mounting surface, it is much easier to connect valves in case pressure fluid is directly supplied from or discharged to the main valve via the valve body. It is also possible to introduce the output of the small size pilot solenoid valve into the pilot port and to use it as a pilot valve for driving the main valve of large capacity.